The Australian Human Rights Commission has made a damning assessment of conditions in the Christmas Island detention centre.

Commission president Gillian Triggs visited the detention facilities on the island in October.

Her report to Immigration Minister Chris Bowen, due to be released on Thursday but obtained by the ABC earlier, describes conditions in the centre as "prison-like".

"The immigration detention facilities on Christmas Island are not appropriate for asylum seekers," the report said.

It goes on to describe the conditions in two of the compounds as "harsh" and inappropriate for accommodating families with children and unaccompanied minors.

The report found there was significant overcrowding in the centre, and said the mixed accommodation of single adult men, unaccompanied minors and families could be in breach of Australia's international obligations under the Convention of the Rights of the Child.

At the time of Professor Triggs's visit, there were 1,989 detainees which included 315 children.

The report noted while there had been some recent improvements including a weekly visit by a psychiatrist, access to a dentist and the construction of a children's playground in one compound, other compounds had no recreational space, grass or shade.